CASTING LACQUER FOR SCREEN PRINTING

Abstract

The present invention relates to a radiation curable screen printing composition for cast-curing comprising one or more compounds comprising radiation curable groups, one or more photoinitiators and one or more rheology modifying agents, which composition has a specific shear rate dependent viscosity; an article comprising a substrate and a coating comprising the radiation curable composition in cured form, wherein the coating is in form of a surface relief structure, a method for producing the article comprising the steps: (i) Providing a casting tool having a relief structure defined in a surface thereof, the relief structure corresponding to the surface relief structure; (ii) Applying to the substrate and/or the relief structure of the casting tool the radiation curable composition; (iii) Cast curing the radiation curable composition by bringing the substrate into contact with a casting tool comprising a relief structure and forming the surface relief structure in the coating composition; and (iv) Radiation curing the coating composition such that the surface relief structure formed of the radiation curable composition is retained on the substrate; a security article comprising at least one inventive substrate; the use of the inventive radiation curable composition for the preparation of a surface relief structure on a substrate; the use of the radiation curable composition for screen printing, preferably rotary screen printing, and preferably subsequent cast curing; and a printing press comprising the radiation curable composition, wherein the printing press is adapted to carry out printing on a web-like or sheet-like substrate, in particular for the production of security articles such as banknotes, comprising a printing unit, preferably a screen-printing unit, the printing press further comprises an in-line casting device comprising a casting tool, wherein the printing unit is designed to apply the radiation curable composition to the substrate and/or the casting tool and the inline-casting device is adapted to replicate and form a surface relief structure in the radiation curable composition.

Claims

1.-26. (canceled)

27. A radiation curable screen printing composition for cast-curing comprising a) one or more compounds comprising radiation curable groups as component A, b) one or more photoinitiators as component B, c) one or more rheology modifying agents as component C, d) optionally one or more defoaming agents as component D, e) optionally one or more adhesion promoters as component E, f) optionally one or more functional material, as component F, which composition has a shear rate dependent viscosity, wherein the viscosity at 35 C. is 15 to 40 PaS at a shear rate of 0.1 s.sup.1 and the viscosity at 35 C. is <0.15 PaS at a shear rate of 1000 s.sup.1, determined according to ISO 3219-2:2021, by a TA Instruments AR-2000 Rheometer using a truncated cone of 60 mm 2 stainless steel and plate geometry, and measurements are conducted in the rotational mode using shear rate control.

28. The radiation curable composition according to claim 27, wherein component A comprises a1) one or more (meth)acrylates, and/or a2) one or more cycloaliphatic epoxides.

29. The radiation curable composition according to claim 28, wherein the one or more (meth)acrylates are a1i) one or more epoxy (meth)acrylates, polyester acrylates and/or polyether acrylates as component A1, and a1ii) one or more monofunctional or multifunctional (meth)acrylates as component A2.

30. The radiation curable composition according to claim 29, wherein the epoxy (meth)acrylates A1 are (meth)acrylates based on aromatic or aliphatic glycidyl ethers, alkylation products of phenol/dicyclopentadiene, phenol-based epoxy novolaks, and cresol-based epoxy novolaks, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, 1,1,2,2-tetrakis[4-(2,3-epoxypropoxy)phenyl]ethane, diglycidyl ether of polypropylene glycol (,-bis(2,3-epoxypropoxy)poly(oxypropylene), and of hydrogenated bisphenol A (2,2-bis[4-(2,3-epoxypropoxy)cyclohexyl]propane), and mixtures thereof.

31. The radiation curable composition according to claim 29, wherein the monofunctional or multifunctional (meth)acrylates A2 are selected from the group consisting of trimethylolpropane triacrylate, trimethylolethane triacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, tetramethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tripropylene glycol diacrylate (TPGDA), dipropylene glycol diacrylate (DPGDA), pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol diacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tripentaerythritol octaacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, dipentaerythritol dimethacrylate, dipentaerythritol tetramethacrylate, tripentaerythritol octamethacrylate, pentaerythritol diitaconate, dipentaerythritol trisitaconate, dipentaerythritol pentaitaconate, dipentaerythritol hexaitaconate, ethylene glycol diacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diitaconate, sorbitol triacrylate, sorbitol tetraacrylate, pentaerythritol-modified triacrylate, sorbitol tetra methacrylate, sorbitol pentaacrylate, sorbitol hexaacrylate, oligoester acrylates and methacrylates, glycerol diacrylate and triacrylate, 1,4-cyclohexane diacrylate, bisacrylates and bismethacrylates of polyethylene glycol with a molecular weight of from 200 to 1500, triacrylate of singly to vigintuply alkoxylated, trimethylolpropane, singly to vigintuply propoxylated glycerol or singly to vigintuply ethoxylated and/or propoxylated pentaerythritol, and mixtures thereof.

32. The radiation curable composition according to claim 28, wherein the one or more cycloaliphatic epoxides comprising at least one cyclohexane group, and at least two epoxide groups is represented by the following formula (I) wherein ##STR00042## Z represents a single bond, a straight- or branchedchain C.sub.1-C.sub.18alkylene group, a divalent alicyclic hydrocarbon group, a cycloalkylene group, CO, OCOO, COO or O.

33. The radiation curable composition according to claim 27, wherein the photoinitiator B is selected from the group consisting of alpha-hydroxy ketone compounds, alpha-alkoxyketone compounds, alpha-aminoketone compounds, benzophenone compounds, acylphosphine oxide compounds, and blends of two or more of the aforementioned compounds.

34. The radiation curable composition according to claim 27, wherein the rheology modifying agent is a non associative rheology modifying agent.

35. The radiation curable composition according to claim 27, wherein the defoaming agent D is a silicon free defoaming agent.

36. The radiation curable composition according to claim 27, wherein the adhesion promoter E is at least one radiation-curable compound having at least one, free acid group or a copolymerizable amine.

37. The radiation curable composition according to claim 29 comprising ai) 1 to 58.5% by weight of component A1, and aii) 40 to 95% by weight of component A2, b) 1 to 10% by weight of component B, c) 0.5 to 3% by weight of component C, d) 0 to 1.5% by weight of component D, e) 0 to 2% by weight of component E, and f) 0 to 50% by weight of component F.

38. The radiation curable composition according to claim 27, wherein the cured composition is transparent.

39. An article comprising a substrate and a coating comprising a radiation cured composition according to claim 27, wherein the coating is in form of a surface relief structure.

40. A method for producing the article according to claim 39 comprising the steps: i) providing a casting tool having a relief structure defined in a surface thereof, the relief structure corresponding to the surface relief structure; ii) applying to the substrate and/or the relief structure of the casting tool the radiation cured composition; iii) casting the radiation cured composition according by bringing the substrate into contact with a casting tool comprising a relief structure and forming the surface relief structure in the coating composition; and iv) radiation curing the coating composition such that the surface relief structure formed of the radiation curable composition is retained on the substrate.

41. The method according to claim 40, wherein the surface relief structure is present in form of a nanostructure or microstructure.

42. The method according to claim 40, comprising the following step after radiation curing in step iv): v) separation of the substrate and the casting tool.

43. The method according to claim 40, wherein i) the casting tool in step i) is provided with a die form, the die form having a surface comprising an arrangement of raised areas and recessed areas defining the raised elements of the surface relief structure; ii) in step ii) the radiation curable composition is applied to the surface of the die form such that the radiation curable composition substantially fills the recessed areas; iii) bringing in step iii) the substrate into contact with the surface of the die form such that it covers the recessed areas; iv) fully or partially curing the coating composition in step iv) such that the radiation curable composition in the recessed areas is removed from said recessed areas and retained on the substrate; and v) separating the substrate from the surface of the die form.

44. The method according to claim 40, wherein the substrate is present in form of sheets.

45. The method according to claim 40, wherein the radiation curable composition is applied to the substrate in step ii) by screen printing.

46. The method according to claim 40, wherein the surface relief structure is one of a diffractive structure; one or more micro-optic element, magnifying elements, faceted elements, reflective elements, or caustic elements; or a macro-structure.

47. Security article comprising at least one article according to claim 39.

48. The security article according to claim 47, wherein the security article is in form of a security document.

49. The security article according to claim 47, wherein the security article is a security thread, strip, insert, foil or patch.

50. A printing press comprising the radiation curable composition according to claim 27, wherein the printing press is adapted to carry out printing on a web-like or sheet-like substrate, in particular for the production of security documents, comprising a printing unit, preferably a screen-printing unit, the printing press further comprises an in-line casting device comprising an casting tool (6) and a radiation source (7), wherein the printing unit is designed to apply the radiation curable composition (2) to the substrate and/or the casting tool and the inline-casting device is adapted to replicate and form a surface relief structure in the radiation curable composition.

Description

[0396] In the following, preferred examples of press configurations are described.

[0397] FIGS. 1 to 3 and 5 to 9 show a web based process for ease of illustration, but the invention is equally applicable to a sheet fed process as illustrated in FIG. 4.

[0398] FIG. 1 illustrates a screen printing unit applying the radiation curable composition to a web. The web is then transferred to an in-line casting device (casting tool) and the radiation curable composition flows into the recesses on the casting tool. The composition is then at least partly cured whilst the substrate is in contact with the casting tool. The cured composition in the form of a surface relief structure on the web is then released from the casting tool and transported to any subsequent processing step.

[0399] The numbers in FIG. 1 have the following meanings:

TABLE-US-00001 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition)

[0400] FIG. 2 illustrates a screen printing unit applying the radiation curable composition to a web as FIG. 1. The web is then transferred to an in-line casting device (casting tool) and the radiation curable composition flows into the recesses on the casting tool. The composition is then partly cured whilst the substrate is in contact with the casting tool. The cured composition in the form of a surface relief structure on the web is then released from the casting tool and post-cured on the resin side of the substrate and then transported to any subsequent processing step.

[0401] The numbers in FIG. 2 have the following meanings:

TABLE-US-00002 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition) 15 Post-cure UV Lamp

[0402] FIG. 3 illustrates a screen printing unit applying the radiation curable composition to a web as FIG. 1. The web is then transferred to an in-line casting device (casting tool) and the radiation curable composition flows into the recesses on the casting tool. The composition is then partly cured whilst the substrate is in contact with the casting tool. The cured composition in the form of a surface relief structure on the web is then released from the casting tool and post-cured on the non-resin side of the substrate and then transported to any subsequent processing step.

[0403] The numbers in FIG. 3 have the following meanings:

TABLE-US-00003 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition) 15 Post-cure UV Lamp

[0404] FIG. 4 illustrates a sheet fed system using the screen and casting unit as explained in the explanation of FIG. 1.

[0405] The numbers in FIG. 4 have the following meanings:

TABLE-US-00004 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 6 Casting Tool 7 UV Lamp 16 Sheet 17 Sheet Gripper 18 Cured Structures (cured composition) on the sheet

[0406] FIG. 5 shows an alternative embodiment where the radiation curable composition is applied directly to the casting tool.

[0407] The numbers in FIG. 5 have the following meanings:

TABLE-US-00005 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition)

[0408] The following FIGS. (6-12) show the addition of further printing units either pre or post the units in FIGS. 1 and 5.

[0409] The further printing units could for example either apply print elements or images that cooperate with the surface relief structures to provide an additional security benefit or they could provide an independent aesthetic design or security feature. The surface relief structure is described above.

[0410] In a preferred embodiment where the surface relief structure is a focusing and/or magnifying element an additional printing unit can be used to form an image array on which the focusing elements are to focus and the magnifying elements are to magnify to generate a secure optical effect.

[0411] In a preferred embodiment the printing press will enable the provision of a focusing element array and an image array located approximately in the focal plane of the focusing element array such that the focusing element array exhibits a substantially focused image of the image array. This focused image may preferably be optically variable and could for example be based on any of the mechanisms detailed below. It should be appreciated the focusing element array and image array could optionally be configured to provide any one or more of these effects, unless otherwise specified: Moire magnifier devices (examples of which are described in EP-A-1695121, WO-A-94/27254, WO-A-2011/107782 and WO2011/107783) make use of an array of focusing elements (such as lenses or mirrors) and a corresponding array of microimages, wherein the pitches of the focusing elements and the array of microimages and/or their relative locations are mismatched with the array of focusing elements such that a magnified version of the microimages is generated due to the moire effect. Each microimage is a complete, miniature version of the image which is ultimately observed, and the array of focusing elements acts to select and magnify a small portion of each underlying microimage, which portions are combined by the human eye such that the whole, magnified image is visualised. This mechanism is sometimes referred to as synthetic magnification. The magnified array appears to move relative to the device upon tilting and can be configured to appear above or below the surface of the device itself. The degree of magnification depends, inter alia, on the degree of pitch mismatch and/or angular mismatch between the focusing element array and the microimage array.

[0412] Integral imaging devices are similar to moire magnifier devices in that an array of microimages is provided under a corresponding array of lenses, each microimage being a miniature version of the image to be displayed. However here there is no mismatch between the lenses and the microimages. Instead a visual effect is created by arranging for each microimage to be a view of the same object but from a different viewpoint. When the device is tilted, different ones of the images are magnified by the lenses such that the impression of a three-dimensional image is given.

[0413] Hybrid devices also exist which combine features of moire magnification devices with those of integral imaging devices. In a pure moire magnification device, the microimages forming the array will generally be identical to one another. Likewise in a pure integral imaging device there will be no mismatch between the arrays, as described above. A hybrid moire magnification/integral imaging device utilises an array of microimages which differ slightly from one another, showing different views of an object, as in an integral imaging device. However, as in a moire magnification device there is a mismatch between the focusing element array and the microimage array, resulting in a synthetically magnified version of the microimage array, due to the moire effect, the magnified microimages having a three-dimensional appearance. Since the visual effect is a result of the moire effect, such hybrid devices are considered a subset of moire magnification devices for the purposes of the present disclosure. In general, therefore, the microimages provided in a moire magnification device should be substantially identical in the sense that they are either exactly the same as one another (pure moire magnifiers) or show the same object/scene but from different viewpoints (hybrid devices).

[0414] Moire magnifiers, integral imaging devices and hybrid devices can all be configured to operate in just one dimension (e.g. utilising cylindrical lenses) or in two dimensions (e.g. comprising a 2D array of spherical or aspherical lenses).

[0415] Lenticular devices on the other hand do not rely upon magnification, synthetic or otherwise. An array of focusing elements, typically cylindrical lenses, overlies a corresponding array of image sections, or slices, each of which depicts only a portion of an image which is to be displayed. Image slices from two or more different images are interleaved and, when viewed through the focusing elements, at each viewing angle, only selected image slices will be directed towards the viewer. In this way, different composite images can be viewed at different angles. However it should be appreciated that no magnification typically takes place and the resulting image which is observed will be of substantially the same size as that to which the underlying image slices are formed. Some examples of lenticular devices are described in U.S. Pat. No. 4,892,336, WO-A2011/051669, WO-A-2011051670, WO-A-2012/027779 and U.S. Pat. No. 6,856,462. More recently, two-dimensional lenticular devices have also been developed and examples of these are disclosed in British patent application numbers 1313362.4 and 1313363.2. Lenticular devices have the advantage that different images can be displayed at different viewing angles, giving rise to the possibility of animation and other striking visual effects which are not possible using the moire magnifier or integral imaging techniques.

[0416] Arrays of lenses or other focusing elements can also be used as a security device on their own (i.e. without a corresponding image array), since they can be used to exhibit a magnified or distorted view of any background they may be placed against, or scene viewed therethrough. This effect cannot be replicated by photocopying or similar.

[0417] FIG. 6 illustrates the use of a gravure printing unit to provide an additional printing step on the opposite side of the substrate. This would enable the use of the focusing elements as described above.

[0418] The numbers in FIG. 6 have the following meanings:

TABLE-US-00006 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition) 9 Gravure Cylinder 10 Chambered Doctor Blade

[0419] FIG. 7 illustrates the use of a gravure printing unit to provide an additional printing step on the same side of the substrate.

[0420] The numbers in FIG. 7 have the following meanings:

TABLE-US-00007 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition) 9 Gravure Cylinder 10 Chambered Doctor Blade

[0421] FIG. 8 illustrates the possibility of using one or more multiple gravure heads prior to the creation of the surface relief structure. The gravure heads can be configured to apply the opacifying layers for the production of a polymer banknote substrate. The gravure heads can also be positioned after the creation of the surface relief structure.

[0422] The numbers in FIG. 8 have the following meanings:

TABLE-US-00008 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition) 9 Gravure Cylinder 10 Chambered Doctor Blade

[0423] FIG. 9 illustrates the use of an offset print process (one single colour) to provide an additional printing step on the opposite side of the substrate.

[0424] The numbers in FIG. 9 have the following meanings:

TABLE-US-00009 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition) 11 Print Blanket 12 Print Plate 13 Inking Rollers 14 Ink Duct

[0425] FIG. 10 illustrates the use of an offset print process (multi coloured) to provide an additional printing step on the opposite side of the substrate.

[0426] The numbers in FIG. 10 have the following meanings:

TABLE-US-00010 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition) 11 Print Blanket 12 Print Plate 13 Inking Rollers 14 Ink Duct

[0427] FIG. 11 illustrates the possibility of using a three colour offset printing process prior to the creation of the surface relief structure. In this embodiment the print is applied on the opposite side of the web to the surface relief structure.

[0428] The numbers in FIG. 11 have the following meanings:

TABLE-US-00011 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition) 11 Print Blanket 12 Print Plate 13 Inking Rollers 14 Ink Duct

[0429] FIG. 12 illustrates the use of an offset print process (one single colour) to provide an additional printing step on the opposite side of the substrate, wherein the additional print is applied when the web is in-between the print blanket and the casting tool and therefore the print process is simultaneous with the casting process.

[0430] The numbers in FIG. 12 have the following meanings:

TABLE-US-00012 1 Screen 2 Radiation curable composition 3 Squeegee 4 Exposed Mesh 5 Uncured radiation curable composition 6 Casting Tool 7 UV Lamp 8 Cured Structures (cured composition) 11 Print Blanket 12 Print Plate 13 Inking Rollers 14 Ink Duct

[0431] The present invention is now described in more details with reference to non-limiting examples.

[0432] The Examples below provide more details for the preparation and properties of the radiation curable compositions according to the present invention.

EXAMPLES

[0433] Below, inventive radiation curable compositions are shown (all components are given in % by weight):

Example 1

TABLE-US-00013 Cast curing lacquer based on a UV-curable composition % by weight Bisphenol A epoxyacrylate with 25% TPGDA.sup.1) 1-35 Dipropylene glycol diacrylate (DPGDA).sup.2) 30-45 Ethoxylated trimethylol propane triacrylate (TMEOPTA).sup.3) 10-50 Rheology additive.sup.4) 0.5-3 Silicone free defoamer.sup.5) 0.5-1.5 Photoinitiator blend: 5-10 Bis(2,4,6-trimethylbenzoyl)phenyl-phosphine oxide / 4-phenyl benz phenone / 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropanoyl)phen- oxy]phenyl}-2-methylpropan-1-one .sup.1)Ebecryl 605 (Epoxyacryl + 25% TPGDA) .sup.2)Laromer DPGDA .sup.3)Laromer LR8863 (TMPEOTA) .sup.4)Rheobyk 7410 .sup.5)EFKA PB2770 indicates data missing or illegible when filed

Example 2 (with Adhesion Promoter)

TABLE-US-00014 Cast curing lacquer based on a UV-curable composition % by weight Bisphenol A epoxyacrylate with 25% TPGDA.sup.1) 1-35 Dipropylene glycol diacrylate (DPGDA).sup.2) 30-45 Ethoxylated trimethylol propane triacrylate (TMEOPTA).sup.3) 10-50 Rheology additive.sup.4) 0.5-3 Adhesion promoter 0.2-2 Silicone free defoamer.sup.5) 0.5-1.5 Photoinitiator blend: 5-10 Bis(2,4,6-trimethylbenzoyl)phenyl-phosphine oxide / 4-phenyl benz phenone / 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropanoyl)phen- oxy]phenyl}-2-methylpropan-1-one .sup.1)Ebecryl 605 (Epoxyacryl + 25% TPGDA) .sup.2)Laromer DPGDA .sup.3)Laromer LR8863 (TMPEOTA) .sup.4)Rheobyk 7410 .sup.5)EFKA PB2770 indicates data missing or illegible when filed

Example 3

TABLE-US-00015 Cast curing lacquer based on a UV-curable composition % by weight Bisphenol A epoxyacrylate with 25% TPGDA.sup.1) 1-35 Dipropylene glycol diacrylate (DPGDA).sup.2) 30-45 Ethoxylated trimethylol propane triacrylate (TMEOPTA).sup.3) 10-50 Rheology additive.sup.4) 0.5-3 Silicone free defoamer.sup.5) 0.5-1.5 Photoinitiator blend: 5-10 Bis(2,4,6-trimethylbenzoyl)phenyl-phosphine oxide / 4-phenyl benz phenone 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropanoyl)phen- oxy]phenyl}-2-methylpropan-1-one .sup.1)Ebecryl 605 (Epoxyacryl + 25% TPGDA) .sup.2)Laromer DPGDA .sup.3)Laromer LR8863 (TMPEOTA) .sup.4)Aerosil 200 .sup.5)EFKA PB2770 indicates data missing or illegible when filed

Example 4 (with Adhesion Promoter)

TABLE-US-00016 Cast curing lacquer based on a UV-curable composition % by weight Bisphenol A epoxyacrylate with 25% TPGDA.sup.1) 1-35 Dipropylene glycol diacrylate (DPGDA).sup.2) 30-45 Ethoxylated trimethylol propane triacrylate (TMEOPTA).sup.3) 10-50 Rheology additive.sup.4) 0.5-3 Adhesion promoter 0.2-2 Silicone free defoamer.sup.5) 0.5-1.5 Photoinitiator blend: 5-10 Bis(2,4,6-trimethylbenzoyl)phenyl-phosphine oxide / 4-phenyl benz phenone / 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropanoyl)phen- oxy]phenyl}-2-methylpropan-1-one .sup.1)Ebecryl 605 (Epoxyacryl + 25% TPGDA) .sup.2)Laromer DPGDA .sup.3)Laromer LR8863 (TMPEOTA) .sup.4)Aerosil 200 .sup.5)EFKA PB2770 indicates data missing or illegible when filed

[0434] The viscosity of the compositions according to examples 1 to 4 at 35 C. is between 15 to 35 Pa S at a shear rate of 0.1 s.sup.1 and the viscosity at 35 C. is <0.15 Pa S at a shear rate of 1000 s.sup.1.

[0435] The viscosity was determined according to ISO 3219-2:2021, by a TA Instruments AR-2000 Rheometer using a truncated cone of 60 mm 2 stainless steel and plate geometry, and measurements are conducted in the rotational mode using shear rate control.

Printing Example

[0436] A 75 micron PET foil (Hostaphan RNK) is overprinted by rotary screen printing with an UV curable composition according to examples 1 to 4. The screen used is a 145 mesh screen. There is no unwanted leakage of the UV curable composition through the screen mesh when in use or at rest, and resin is only passed through the screen when printed in normal operation.

[0437] Subsequently the UV curable composition prior to curing is cast with a temperature regulated steel based roller that is electroless or galvanically plated with nickel, which has 12-14% phosphorous content, and contains a structure corresponding to an array of cylindrical lenses with a typical radius of 17 micron and a typical pitch of 60 micron. The casting is carried out under pressure, in a range 100-1000 N/m) with the cast roller heated to 50deg C.

[0438] The UV resin is cured whilst in contact with the casting tool, the curing is carried out by a Phoseon UV LED lamp, namely a FireJet FJ200 with a lamp size of 15020 mm at 385 nm wavelength, with a peak irradiance of 12 W/cm2. The lamp is ran at 100% power intensity. The press is ran at a speed of 80 m/m.

[0439] The process and separation of the substrate from the casting tool can be carried out without any difficulties, producing the lenticular lens structure on the substrate.